Kelda Water choose SPS DAF for RMB Chivenor Devon

12 Aug 2013

Siltbuster Process Solutions (SPS) has just successfully completed a Dissolved Air Flotation (DAF) hire project for Kelda Water at RMB Chivenor in North Devon. SPS’s Technical Manager Dr Chris Bullen explains the project involved providing a temporary solids/liquid separation system whilst the existing half bridge clarifier was being refurbished.

Normally solids liquid/separation on an Activated Sludge Plant is carried out using a clarifier/thickener unit commented Dr Bullen, however our mobile Siltbuster D100 Dissolved Air Floatation (DAF) unit offered a solution that addressed the numerous constraints of the project.

These included the availability of a solution at short notice; simple ‘plug and play’ installation and operation; compact size – given the limited space available on site; and finally, proven technology that works. As well as the DAF, SPS offers access to experienced process support throughout the life of the installation.

Whilst the use of DAF for sludge thickening applications is well documented, DAFs are less frequently used for permanent activated sludge clarification simply because of the perceived on-going operational cost of the whitewater system. However DAFs are ideal for this sort of temporary application, comments Dr Bullen, because you get a lot of treatment capacity in a relatively small area. At Chivenor our D100 unit which measured 6m long x 2.4m wide replaced a 9.5m (71m²) diameter conventional clarifier.

Importantly with DAF the operator is in control of the solids/liquid separation process. By varying the air/solids ratio and the scraper speed, the supernatant clarity and the density of the floated off sludge can be controlled – whereas the performance of a conventional clarifier is dictated solely by the settlement characteristics of the sludge.

This can be particularly advantageous when dealing with bulking sludges and other emergency situations. For example, at Chivenor, the D100 was fed at a rate of 72m³/hr of mixed liquors with a suspended solids concentration of 2500mg/l and produced a final effluent of <30mg/l and a return activated sludge concentration of 3% solids.